The present invention relates to a non-contact type seal device for a turbocharger, and more particularly to a non-contact type seal device for preventing lubricating oil from leaking into a compressor chamber of a turbocharger.
Referring to FIGS. 1 and 2, the general arrangement of a prior art turbocharger will be described.
A housing 1 of the turbocharger is constituted by a turbine housing 2, a bearing housing 3, and a compressor housing 4. A rotor shaft 7, having a turbine wheel 5 and a compressor wheel 6 provided at its opposite ends, is rotatably supported by the bearing housing 3 through full-float bearings 8 and a thrust bearing 9. Lubricating oil for the full-float bearings 8 and the thrust bearing 9 is supplied into the bearing housing 3. A non-contact type seal device for preventing the lubricating oil from entering a compressor chamber 1a is also provided.
Referring specifically to FIG. 2, the non-contact type seal device includes a ring 11 provided on an inner peripheral surface 10a of a retainer 10, the latter being provided on the compressor chamber 1a side of the housing 1, and an annular groove 13 for receiving the ring 11 is formed in the outer peripheral surface 12a of the collar 12 fixed on the fitting portion side of a compressor wheel of the rotor shaft 7 by press-fitting or fastening. A gap is formed between the outer peripheral surface 12a of the collar 12 and the inner peripheral surface 10a of a retainer 10, and another gap is formed between the inner surface of the annular groove 13 and each of the opposite end surfaces and inner peripheral surface of the ring 11.
Although a so-called labyrinth seal structure is provided to prevent lubricating oil from entering the compression chamber 1a, there is a possibility that the lubricating oil will enter the compressor chamber 1a from a lubricating oil chamber 1c through the gap between the annular groove 13 of the collar 12 and the ring 11 of the inner peripheral surface 10a of the retainer 10 because of the pressure difference which exists between a turbine chamber 16 and the compressor chamber 1a under conditions of high negative pressure. This leakage causes an increase in consumption of the lubricating oil.